Navigating multi-way stop intersections with an autonomous vehicle

ABSTRACT

The subject matter described in this specification is directed to a system and techniques for operating an autonomous vehicle (AV) at a multi-way stop intersection. After detecting the AV is at a primary stopline of the multi-way stop intersection, a planned travel path though the multi-way stop intersection is obtained. If the planned travel path of the AV through the multi-way stop intersection satisfies a set of one or more clearance criteria, the AV proceeds past the primary stopline. The clearance criteria include a criterion that is satisfied in response to detecting the AV is clear to safely merge into a travel lane corresponding to the planned travel path.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/912,417, filed Oct. 8, 2019, entitled “NAVIGATING MULTI-WAY STOP INTERSECTIONS WITH AN AUTONOMOUS VEHICLE,” the entire contents of which are hereby incorporated by reference.

FIELD

This description relates to autonomous vehicles, and more specifically to autonomous vehicles navigating multi-way stop intersections.

BACKGROUND

Autonomous vehicles can be used to transport people and/or cargo (e.g., packages, objects, or other items) from one location to another. For example, an autonomous vehicle can navigate to the location of a person, wait for the person to board the autonomous vehicle, and navigate to a specified destination (e.g., a location selected by the person). To navigate in the environment, these autonomous vehicles are equipped with various types of sensors to detect objects in the surroundings.

SUMMARY

The subject matter described in this specification is directed to a system and techniques for navigating an autonomous vehicle through a multi-way stop intersection. Generally, the system is configured to instruct the autonomous vehicle to wait at a stopline of the multi-way stop intersection until it is safe for the autonomous vehicle to proceed past the stopline.

In particular, an example technique includes: while a first vehicle is operating in an autonomous mode: detecting, using a processing circuit, the first vehicle is at a primary stopline of a multi-way stop intersection; obtaining, using the processing circuit, a planned travel path though the multi-way stop intersection; and in response to detecting that the first vehicle is at a primary stopline of a multi-way stop intersection: in accordance with a determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies a set of one or more clearance criteria, instructing, using a control circuit, the first vehicle to proceed past the primary stopline, wherein the set of one or more clearance criteria include a criterion that is satisfied in response to detecting the first vehicle is clear to safely merge into a travel lane corresponding to the planned travel path; and in accordance with a determination that the planned travel path of the first vehicle through the multi-way stop intersection does not satisfy the set of one or more clearance criteria, instructing, using the control circuit, the first vehicle to forgo proceeding past the primary stopline.

Another example technique includes: while a first vehicle is operating in an autonomous mode at a multi-way stop intersection and has a highest precedence at the multi-way stop intersection: detecting, using a processing circuit, movement of a second vehicle at the intersection, the second vehicle having an expected travel path through the intersection that intersects a planned travel path of the first vehicle through the intersection; and in accordance with a determination, based on the detected movement of the second vehicle, that the second vehicle is expected to exit the intersection, instructing, using a control circuit, the first vehicle to proceed into the intersection before the second vehicle exits the intersection.

These and other aspects, features, and implementations can be expressed as methods, apparatuses, systems, components, program products, means or steps for performing a function, and in other ways.

These and other aspects, features, and implementations will become apparent from the following descriptions, including the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of an autonomous vehicle having autonomous capability.

FIG. 2 illustrates an example “cloud” computing environment.

FIG. 3 illustrates a computer system.

FIG. 4 shows an example architecture for an autonomous vehicle.

FIG. 5 shows an example of inputs and outputs that may be used by a perception module.

FIG. 6 shows an example of a LiDAR system.

FIG. 7 shows the LiDAR system in operation.

FIG. 8 shows the operation of the LiDAR system in additional detail.

FIG. 9 shows a block diagram of the relationships between inputs and outputs of a planning module.

FIG. 10 shows a directed graph used in path planning.

FIG. 11 shows a block diagram of the inputs and outputs of a control module.

FIG. 12 shows a block diagram of the inputs, outputs, and components of a controller.

FIGS. 13A-13L illustrate examples of an autonomous vehicle navigating a multi-way stop intersection.

FIG. 14 is a flow chart of an example process for navigating a multi-way stop intersection.

FIG. 15 is a flow chart of another example process for navigating a multi-way stop intersection.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerous specific details are set forth. It will be apparent, however, that some embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the described embodiments.

In the drawings, specific arrangements or orderings of schematic elements, such as those representing devices, modules, instruction blocks and data elements, are shown for ease of description. However, it should be understood by those skilled in the art that the specific ordering or arrangement of the schematic elements in the drawings is not meant to imply that a particular order or sequence of processing, or separation of processes, is required. Further, the inclusion of a schematic element in a drawing is not meant to imply that such element is required in all embodiments or that the features represented by such element may not be included in or combined with other elements in some embodiments.

Further, in the drawings, where connecting elements, such as solid or dashed lines or arrows, are used to illustrate a connection, relationship, or association between or among two or more other schematic elements, the absence of any such connecting elements is not meant to imply that no connection, relationship, or association can exist. In other words, some connections, relationships, or associations between elements are not shown in the drawings so as not to obscure the disclosure. In addition, for ease of illustration, a single connecting element is used to represent multiple connections, relationships or associations between elements. For example, where a connecting element represents a communication of signals, data, or instructions, it should be understood by those skilled in the art that such element represents one or multiple signal paths (e.g., a bus), as may be needed, to affect the communication.

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

Several features are described hereafter that can each be used independently of one another or with any combination of other features. However, any individual feature may not address any of the problems discussed above or might only address one of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein. Although headings are provided, information related to a particular heading, but not found in the section having that heading, may also be found elsewhere in this description. Embodiments are described herein according to the following outline:

-   -   1. General Overview     -   2. Hardware Overview     -   3. Autonomous Vehicle Architecture     -   4. Autonomous Vehicle Inputs     -   5. Autonomous Vehicle Planning     -   6. Autonomous Vehicle Control     -   7. Computing System for Object Detection Using Pillars     -   8. Example Point Clouds and Pillars     -   9. Example Process for Detecting Objects and Operating the         Vehicle Based on the Detection of the Objects         General Overview

Autonomous vehicles driving in complex environments (e.g., an urban environment) pose a great technological challenge. In order for autonomous vehicles to navigate these environments, the vehicles detect various types of objects such as vehicles, pedestrians, and bikes in real-time using sensors such as LIDAR or RADAR. When an autonomous vehicle encounters a multi-way stop intersection, the autonomous vehicle uses sensors to detect other vehicles at the intersection, and determine when it is safe for the autonomous vehicle to proceed into the intersection. In some circumstances, other vehicles at the multi-way stop intersection may move toward the intersection when they do not intend to proceed through the intersection until after one or more other vehicles (e.g., another vehicle may slowly crawl forward when they are next to have the right-of-way through the intersection to signal their intent). In other circumstances, another vehicle may proceed into the intersection when they do not have the right-of-way according to local traffic regulations (e.g., another vehicle may not notice that the autonomous vehicle arrived earlier at the intersection). The disclosed embodiments include a system and techniques that allow an autonomous vehicle to navigate a multi-way stop intersection in these and other circumstances.

In particular, the system and techniques described herein allow an autonomous vehicle to navigate a multi-way stop intersection by determining whether the autonomous vehicle is clear to safely merge into a travel lane (e.g., a lane of the roadway) corresponding to (e.g., overlapping, nearest to) a planned travel path of the autonomous vehicle. By using safe merging techniques at a multi-way stop intersection, the autonomous vehicle can join the travel lane at a safe distance behind another vehicle traveling along the same path, without blocking paths of other vehicles. In some embodiments, the merging techniques described herein for multi-way stop intersections are the same or similar merging techniques used when changing lanes or merging on a multi-lane roadway.

Furthermore, in some embodiments, the system and techniques described herein allow an autonomous vehicle to signal its intent to other vehicles at the multi-way stop intersection by proceeding into the intersection before another vehicle has fully exited the intersection. This early movement of the autonomous vehicle indicates to other vehicles that the autonomous vehicle is next to have the right-of-way at the intersection, and may prevent other vehicles from proceeding out-of-turn.

Hardware Overview

FIG. 1 shows an example of an autonomous vehicle 100 having autonomous capability.

As used herein, the term “autonomous capability” refers to a function, feature, or facility that enables a vehicle to be partially or fully operated without real-time human intervention, including without limitation fully autonomous vehicles, highly autonomous vehicles, and conditionally autonomous vehicles.

As used herein, an autonomous vehicle (AV) is a vehicle that possesses autonomous capability.

As used herein, “vehicle” includes means of transportation of goods or people. For example, cars, buses, trains, airplanes, drones, trucks, boats, ships, submersibles, dirigibles, etc. A driverless car is an example of a vehicle.

As used herein, “trajectory” refers to a path or route to navigate an AV from a first spatiotemporal location to second spatiotemporal location. In an embodiment, the first spatiotemporal location is referred to as the initial or starting location and the second spatiotemporal location is referred to as the destination, final location, goal, goal position, or goal location. In some examples, a trajectory is made up of one or more segments (e.g., sections of road) and each segment is made up of one or more blocks (e.g., portions of a lane or intersection). In an embodiment, the spatiotemporal locations correspond to real world locations. For example, the spatiotemporal locations are pick up or drop-off locations to pick up or drop-off persons or goods.

As used herein, “sensor(s)” includes one or more hardware components that detect information about the environment surrounding the sensor. Some of the hardware components can include sensing components (e.g., image sensors, biometric sensors), transmitting and/or receiving components (e.g., laser or radio frequency wave transmitters and receivers), electronic components such as analog-to-digital converters, a data storage device (such as a RAM and/or a nonvolatile storage), software or firmware components and data processing components such as an ASIC (application-specific integrated circuit), a microprocessor and/or a microcontroller.

As used herein, a “scene description” is a data structure (e.g., list) or data stream that includes one or more classified or labeled objects detected by one or more sensors on the AV vehicle or provided by a source external to the AV.

As used herein, a “road” is a physical area that can be traversed by a vehicle, and may correspond to a named thoroughfare (e.g., city street, interstate freeway, etc.) or may correspond to an unnamed thoroughfare (e.g., a driveway in a house or office building, a section of a parking lot, a section of a vacant lot, a dirt path in a rural area, etc.). Because some vehicles (e.g., 4-wheel-drive pickup trucks, sport utility vehicles, etc.) are capable of traversing a variety of physical areas not specifically adapted for vehicle travel, a “road” may be a physical area not formally defined as a thoroughfare by any municipality or other governmental or administrative body.

As used herein, a “lane” is a portion of a road that can be traversed by a vehicle, and may correspond to most or all of the space between lane markings, or may correspond to only some (e.g., less than 50%) of the space between lane markings. For example, a road having lane markings spaced far apart might accommodate two or more vehicles between the markings, such that one vehicle can pass the other without traversing the lane markings, and thus could be interpreted as having a lane narrower than the space between the lane markings, or having two lanes between the lane markings. A lane could also be interpreted in the absence of lane markings. For example, a lane may be defined based on physical features of an environment, e.g., rocks and trees along a thoroughfare in a rural area.

“One or more” includes a function being performed by one element, a function being performed by more than one element, e.g., in a distributed fashion, several functions being performed by one element, several functions being performed by several elements, or any combination of the above.

It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first contact could be termed a second contact, and, similarly, a second contact could be termed a first contact, without departing from the scope of the various described embodiments. The first contact and the second contact are both contacts, but they are not the same contact, unless specified otherwise.

The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this description, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, the term “if” is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context.

As used herein, an AV system refers to the AV along with the array of hardware, software, stored data, and data generated in real-time that supports the operation of the AV. In an embodiment, the AV system is incorporated within the AV. In an embodiment, the AV system is spread across several locations. For example, some of the software of the AV system is implemented on a cloud computing environment similar to cloud computing environment 200 described below with respect to FIG. 2 .

In general, this document describes technologies applicable to any vehicles that have one or more autonomous capabilities including fully autonomous vehicles, highly autonomous vehicles, and conditionally autonomous vehicles, such as so-called Level 5, Level 4 and Level 3 vehicles, respectively (see SAE International's standard J3016: Taxonomy and Definitions for Terms Related to On-Road Motor Vehicle Automated Driving Systems, which is incorporated by reference in its entirety, for more details on the classification of levels of autonomy in vehicles). The technologies described in this document are also applicable to partially autonomous vehicles and driver assisted vehicles, such as so-called Level 2 and Level 1 vehicles (see SAE International's standard J3016: Taxonomy and Definitions for Terms Related to On-Road Motor Vehicle Automated Driving Systems). In an embodiment, one or more of the Level 1, 2, 3, 4 and 5 vehicle systems may automate certain vehicle operations (e.g., steering, braking, and using maps) under certain operating conditions based on processing of sensor inputs. The technologies described in this document can benefit vehicles in any levels, ranging from fully autonomous vehicles to human-operated vehicles.

Referring to FIG. 1 , an AV system 120 operates the AV 100 along a trajectory 198 through an environment 190 to a destination 199 (sometimes referred to as a final location) while avoiding objects (e.g., natural obstructions 191, vehicles 193, pedestrians 192, cyclists, and other obstacles) and obeying rules of the road (e.g., rules of operation or driving preferences).

In an embodiment, the AV system 120 includes devices 101 that are instrumented to receive and act on operational commands from the computer processors 146. In an embodiment, computing processors 146 are similar to the processor 304 described below in reference to FIG. 3 . Examples of devices 101 include a steering control 102, brakes 103, gears, accelerator pedal or other acceleration control mechanisms, windshield wipers, side-door locks, window controls, and turn-indicators.

In an embodiment, the AV system 120 includes sensors 121 for measuring or inferring properties of state or condition of the AV 100, such as the AV's position, linear and angular velocity and acceleration, and heading (e.g., an orientation of the leading end of AV 100). Example of sensors 121 are GPS, inertial measurement units (IMU) that measure both vehicle linear accelerations and angular rates, wheel speed sensors for measuring or estimating wheel slip ratios, wheel brake pressure or braking torque sensors, engine torque or wheel torque sensors, and steering angle and angular rate sensors.

In an embodiment, the sensors 121 also include sensors for sensing or measuring properties of the AV's environment. For example, monocular or stereo video cameras 122 in the visible light, infrared or thermal (or both) spectra, LiDAR 123, RADAR, ultrasonic sensors, time-of-flight (TOF) depth sensors, speed sensors, temperature sensors, humidity sensors, and precipitation sensors.

In an embodiment, the AV system 120 includes a data storage unit 142 and memory 144 for storing machine instructions associated with computer processors 146 or data collected by sensors 121. In an embodiment, the data storage unit 142 is similar to the ROM 308 or storage device 310 described below in relation to FIG. 3 . In an embodiment, memory 144 is similar to the main memory 306 described below. In an embodiment, the data storage unit 142 and memory 144 store historical, real-time, and/or predictive information about the environment 190. In an embodiment, the stored information includes maps, driving performance, traffic congestion updates or weather conditions. In an embodiment, data relating to the environment 190 is transmitted to the AV 100 via a communications channel from a remotely located database 134.

In an embodiment, the AV system 120 includes communications devices 140 for communicating measured or inferred properties of other vehicles' states and conditions, such as positions, linear and angular velocities, linear and angular accelerations, and linear and angular headings to the AV 100. These devices include Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communication devices and devices for wireless communications over point-to-point or ad hoc networks or both. In an embodiment, the communications devices 140 communicate across the electromagnetic spectrum (including radio and optical communications) or other media (e.g., air and acoustic media). A combination of Vehicle-to-Vehicle (V2V) Vehicle-to-Infrastructure (V2I) communication (and, in some embodiments, one or more other types of communication) is sometimes referred to as Vehicle-to-Everything (V2X) communication. V2X communication typically conforms to one or more communications standards for communication with, between, and among autonomous vehicles.

In an embodiment, the communication devices 140 include communication interfaces. For example, wired, wireless, WiMAX, WiFi, Bluetooth, satellite, cellular, optical, near field, infrared, or radio interfaces. The communication interfaces transmit data from a remotely located database 134 to AV system 120. In an embodiment, the remotely located database 134 is embedded in a cloud computing environment 200 as described in FIG. 2 . The communication interfaces 140 transmit data collected from sensors 121 or other data related to the operation of AV 100 to the remotely located database 134. In an embodiment, communication interfaces 140 transmit information that relates to teleoperations to the AV 100. In some embodiments, the AV 100 communicates with other remote (e.g., “cloud”) servers 136.

In an embodiment, the remotely located database 134 also stores and transmits digital data (e.g., storing data such as road and street locations). Such data is stored on the memory 144 on the AV 100, or transmitted to the AV 100 via a communications channel from the remotely located database 134.

In an embodiment, the remotely located database 134 stores and transmits historical information about driving properties (e.g., speed and acceleration profiles) of vehicles that have previously traveled along trajectory 198 at similar times of day. In one implementation, such data may be stored on the memory 144 on the AV 100, or transmitted to the AV 100 via a communications channel from the remotely located database 134.

Computing devices 146 located on the AV 100 algorithmically generate control actions based on both real-time sensor data and prior information, allowing the AV system 120 to execute its autonomous driving capabilities.

In an embodiment, the AV system 120 includes computer peripherals 132 coupled to computing devices 146 for providing information and alerts to, and receiving input from, a user (e.g., an occupant or a remote user) of the AV 100. In an embodiment, peripherals 132 are similar to the display 312, input device 314, and cursor controller 316 discussed below in reference to FIG. 3 . The coupling is wireless or wired. Any two or more of the interface devices may be integrated into a single device.

FIG. 2 illustrates an example “cloud” computing environment. Cloud computing is a model of service delivery for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines, and services). In typical cloud computing systems, one or more large cloud data centers house the machines used to deliver the services provided by the cloud. Referring now to FIG. 2 , the cloud computing environment 200 includes cloud data centers 204 a, 204 b, and 204 c that are interconnected through the cloud 202. Data centers 204 a, 204 b, and 204 c provide cloud computing services to computer systems 206 a, 206 b, 206 c, 206 d, 206 e, and 206 f connected to cloud 202.

The cloud computing environment 200 includes one or more cloud data centers. In general, a cloud data center, for example the cloud data center 204 a shown in FIG. 2 , refers to the physical arrangement of servers that make up a cloud, for example the cloud 202 shown in FIG. 2 , or a particular portion of a cloud. For example, servers are physically arranged in the cloud datacenter into rooms, groups, rows, and racks. A cloud datacenter has one or more zones, which include one or more rooms of servers. Each room has one or more rows of servers, and each row includes one or more racks. Each rack includes one or more individual server nodes. In some implementation, servers in zones, rooms, racks, and/or rows are arranged into groups based on physical infrastructure requirements of the datacenter facility, which include power, energy, thermal, heat, and/or other requirements. In an embodiment, the server nodes are similar to the computer system described in FIG. 3 . The data center 204 a has many computing systems distributed through many racks.

The cloud 202 includes cloud data centers 204 a, 204 b, and 204 c along with the network and networking resources (for example, networking equipment, nodes, routers, switches, and networking cables) that interconnect the cloud data centers 204 a, 204 b, and 204 c and help facilitate the computing systems' 206 a-f access to cloud computing services. In an embodiment, the network represents any combination of one or more local networks, wide area networks, or internetworks coupled using wired or wireless links deployed using terrestrial or satellite connections. Data exchanged over the network, is transferred using any number of network layer protocols, such as Internet Protocol (IP), Multiprotocol Label Switching (MPLS), Asynchronous Transfer Mode (ATM), Frame Relay, etc. Furthermore, in embodiments where the network represents a combination of multiple sub-networks, different network layer protocols are used at each of the underlying sub-networks. In some embodiments, the network represents one or more interconnected internetworks, such as the public Internet.

The computing systems 206 a-f or cloud computing services consumers are connected to the cloud 202 through network links and network adapters. In an embodiment, the computing systems 206 a-f are implemented as various computing devices, for example servers, desktops, laptops, tablet, smartphones, Internet of Things (IoT) devices, autonomous vehicles (including, cars, drones, shuttles, trains, buses, etc.) and consumer electronics. In an embodiment, the computing systems 206 a-f are implemented in or as a part of other systems.

FIG. 3 illustrates a computer system 300. In an implementation, the computer system 300 is a special purpose computing device. The special-purpose computing device is hard-wired to perform the techniques or includes digital electronic devices such as one or more application-specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs) that are persistently programmed to perform the techniques, or may include one or more general purpose hardware processors programmed to perform the techniques pursuant to program instructions in firmware, memory, other storage, or a combination. Such special-purpose computing devices may also combine custom hard-wired logic, ASICs, or FPGAs with custom programming to accomplish the techniques. In various embodiments, the special-purpose computing devices are desktop computer systems, portable computer systems, handheld devices, network devices or any other device that incorporates hard-wired and/or program logic to implement the techniques.

In an embodiment, the computer system 300 includes a bus 302 or other communication mechanism for communicating information, and a hardware processor 304 coupled with a bus 302 for processing information. The hardware processor 304 is, for example, a general-purpose microprocessor. The computer system 300 also includes a main memory 306, such as a random-access memory (RAM) or other dynamic storage device, coupled to the bus 302 for storing information and instructions to be executed by processor 304. In one implementation, the main memory 306 is used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor 304. Such instructions, when stored in non-transitory storage media accessible to the processor 304, render the computer system 300 into a special-purpose machine that is customized to perform the operations specified in the instructions.

In an embodiment, the computer system 300 further includes a read only memory (ROM) 308 or other static storage device coupled to the bus 302 for storing static information and instructions for the processor 304. A storage device 310, such as a magnetic disk, optical disk, solid-state drive, or three-dimensional cross point memory is provided and coupled to the bus 302 for storing information and instructions.

In an embodiment, the computer system 300 is coupled via the bus 302 to a display 312, such as a cathode ray tube (CRT), a liquid crystal display (LCD), plasma display, light emitting diode (LED) display, or an organic light emitting diode (OLED) display for displaying information to a computer user. An input device 314, including alphanumeric and other keys, is coupled to bus 302 for communicating information and command selections to the processor 304. Another type of user input device is a cursor controller 316, such as a mouse, a trackball, a touch-enabled display, or cursor direction keys for communicating direction information and command selections to the processor 304 and for controlling cursor movement on the display 312. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x-axis) and a second axis (e.g., y-axis), that allows the device to specify positions in a plane.

According to one embodiment, the techniques herein are performed by the computer system 300 in response to the processor 304 executing one or more sequences of one or more instructions contained in the main memory 306. Such instructions are read into the main memory 306 from another storage medium, such as the storage device 310. Execution of the sequences of instructions contained in the main memory 306 causes the processor 304 to perform the process steps described herein. In alternative embodiments, hard-wired circuitry is used in place of or in combination with software instructions.

The term “storage media” as used herein refers to any non-transitory media that store data and/or instructions that cause a machine to operate in a specific fashion. Such storage media includes non-volatile media and/or volatile media. Non-volatile media includes, for example, optical disks, magnetic disks, solid-state drives, or three-dimensional cross point memory, such as the storage device 310. Volatile media includes dynamic memory, such as the main memory 306. Common forms of storage media include, for example, a floppy disk, a flexible disk, hard disk, solid-state drive, magnetic tape, or any other magnetic data storage medium, a CD-ROM, any other optical data storage medium, any physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, NV-RAM, or any other memory chip or cartridge.

Storage media is distinct from but may be used in conjunction with transmission media. Transmission media participates in transferring information between storage media. For example, transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise the bus 302. Transmission media can also take the form of acoustic or light waves, such as those generated during radio-wave and infrared data communications.

In an embodiment, various forms of media are involved in carrying one or more sequences of one or more instructions to the processor 304 for execution. For example, the instructions are initially carried on a magnetic disk or solid-state drive of a remote computer. The remote computer loads the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to the computer system 300 receives the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector receives the data carried in the infrared signal and appropriate circuitry places the data on the bus 302. The bus 302 carries the data to the main memory 306, from which processor 304 retrieves and executes the instructions. The instructions received by the main memory 306 may optionally be stored on the storage device 310 either before or after execution by processor 304.

The computer system 300 also includes a communication interface 318 coupled to the bus 302. The communication interface 318 provides a two-way data communication coupling to a network link 320 that is connected to a local network 322. For example, the communication interface 318 is an integrated service digital network (ISDN) card, cable modem, satellite modem, or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, the communication interface 318 is a local area network (LAN) card to provide a data communication connection to a compatible LAN. In some implementations, wireless links are also implemented. In any such implementation, the communication interface 318 sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information.

The network link 320 typically provides data communication through one or more networks to other data devices. For example, the network link 320 provides a connection through the local network 322 to a host computer 324 or to a cloud data center or equipment operated by an Internet Service Provider (ISP) 326. The ISP 326 in turn provides data communication services through the world-wide packet data communication network now commonly referred to as the “Internet” 328. The local network 322 and Internet 328 both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on the network link 320 and through the communication interface 318, which carry the digital data to and from the computer system 300, are example forms of transmission media. In an embodiment, the network 320 contains the cloud 202 or a part of the cloud 202 described above.

The computer system 300 sends messages and receives data, including program code, through the network(s), the network link 320, and the communication interface 318. In an embodiment, the computer system 300 receives code for processing. The received code is executed by the processor 304 as it is received, and/or stored in storage device 310, or other non-volatile storage for later execution.

Autonomous Vehicle Architecture

FIG. 4 shows an example architecture 400 for an autonomous vehicle (e.g., the AV 100 shown in FIG. 1 ). The architecture 400 includes a perception module 402 (sometimes referred to as a perception circuit), a planning module 404 (sometimes referred to as a planning circuit), a control module 406 (sometimes referred to as a control circuit), a localization module 408 (sometimes referred to as a localization circuit), and a database module 410 (sometimes referred to as a database circuit). Each module plays a role in the operation of the AV 100. Together, the modules 402, 404, 406, 408, and 410 may be part of the AV system 120 shown in FIG. 1 . In some embodiments, any of the modules 402, 404, 406, 408, and 410 is a combination of computer software (e.g., executable code stored on a computer-readable medium) and computer hardware (e.g., one or more microprocessors, microcontrollers, application-specific integrated circuits [ASICs]), hardware memory devices, other types of integrated circuits, other types of computer hardware, or a combination of any or all of these things).

In use, the planning module 404 receives data representing a destination 412 and determines data representing a trajectory 414 (sometimes referred to as a route) that can be traveled by the AV 100 to reach (e.g., arrive at) the destination 412. In order for the planning module 404 to determine the data representing the trajectory 414, the planning module 404 receives data from the perception module 402, the localization module 408, and the database module 410.

The perception module 402 identifies nearby physical objects using one or more sensors 121, e.g., as also shown in FIG. 1 . The objects are classified (e.g., grouped into types such as pedestrian, bicycle, automobile, traffic sign, etc.) and a scene description including the classified objects 416 is provided to the planning module 404.

The planning module 404 also receives data representing the AV position 418 from the localization module 408. The localization module 408 determines the AV position by using data from the sensors 121 and data from the database module 410 (e.g., a geographic data) to calculate a position. For example, the localization module 408 uses data from a GNSS (Global Navigation Satellite System) sensor and geographic data to calculate a longitude and latitude of the AV. In an embodiment, data used by the localization module 408 includes high-precision maps of the roadway geometric properties, maps describing road network connectivity properties, maps describing roadway physical properties (such as traffic speed, traffic volume, the number of vehicular and cyclist traffic lanes, lane width, lane traffic directions, or lane marker types and locations, or combinations of them), and maps describing the spatial locations of road features such as crosswalks, traffic signs or other travel signals of various types.

The control module 406 receives the data representing the trajectory 414 and the data representing the AV position 418 and operates the control functions 420 a-c (e.g., steering, throttling, braking, ignition) of the AV in a manner that will cause the AV 100 to travel the trajectory 414 to the destination 412. For example, if the trajectory 414 includes a left turn, the control module 406 will operate the control functions 420 a-c in a manner such that the steering angle of the steering function will cause the AV 100 to turn left and the throttling and braking will cause the AV 100 to pause and wait for passing pedestrians or vehicles before the turn is made.

Autonomous Vehicle Inputs

FIG. 5 shows an example of inputs 502 a-d (e.g., sensors 121 shown in FIG. 1 ) and outputs 504 a-d (e.g., sensor data) that is used by the perception module 402 (FIG. 4 ). One input 502 a is a LiDAR (Light Detection and Ranging) system (e.g., LiDAR 123 shown in FIG. 1 ). LiDAR is a technology that uses light (e.g., bursts of light such as infrared light) to obtain data about physical objects in its line of sight. A LiDAR system produces LiDAR data as output 504 a. For example, LiDAR data is collections of 3D or 2D points (also known as a point clouds) that are used to construct a representation of the environment 190.

Another input 502 b is a RADAR system. RADAR is a technology that uses radio waves to obtain data about nearby physical objects. RADARs can obtain data about objects not within the line of sight of a LiDAR system. A RADAR system 502 b produces RADAR data as output 504 b. For example, RADAR data are one or more radio frequency electromagnetic signals that are used to construct a representation of the environment 190.

Another input 502 c is a camera system. A camera system uses one or more cameras (e.g., digital cameras using a light sensor such as a charge-coupled device [CCD]) to obtain information about nearby physical objects. A camera system produces camera data as output 504 c. Camera data often takes the form of image data (e.g., data in an image data format such as RAW, JPEG, PNG, etc.). In some examples, the camera system has multiple independent cameras, e.g., for the purpose of stereopsis (stereo vision), which enables the camera system to perceive depth. Although the objects perceived by the camera system are described here as “nearby,” this is relative to the AV. In use, the camera system may be configured to “see” objects far, e.g., up to a kilometer or more ahead of the AV. Accordingly, the camera system may have features such as sensors and lenses that are optimized for perceiving objects that are far away.

Another input 502 d is a traffic light detection (TLD) system. A TLD system uses one or more cameras to obtain information about traffic lights, street signs, and other physical objects that provide visual navigation information. A TLD system produces TLD data as output 504 d. TLD data often takes the form of image data (e.g., data in an image data format such as RAW, JPEG, PNG, etc.). A TLD system differs from a system incorporating a camera in that a TLD system uses a camera with a wide field of view (e.g., using a wide-angle lens or a fish-eye lens) in order to obtain information about as many physical objects providing visual navigation information as possible, so that the AV 100 has access to all relevant navigation information provided by these objects. For example, the viewing angle of the TLD system may be about 120 degrees or more.

In some embodiments, outputs 504 a-d are combined using a sensor fusion technique. Thus, either the individual outputs 504 a-d are provided to other systems of the AV 100 (e.g., provided to a planning module 404 as shown in FIG. 4 ), or the combined output can be provided to the other systems, either in the form of a single combined output or multiple combined outputs of the same type (e.g., using the same combination technique or combining the same outputs or both) or different types type (e.g., using different respective combination techniques or combining different respective outputs or both). In some embodiments, an early fusion technique is used. An early fusion technique is characterized by combining outputs before one or more data processing steps are applied to the combined output. In some embodiments, a late fusion technique is used. A late fusion technique is characterized by combining outputs after one or more data processing steps are applied to the individual outputs.

FIG. 6 shows an example of a LiDAR system 602 (e.g., the input 502 a shown in FIG. 5 ). The LiDAR system 602 emits light 604 a-c from a light emitter 606 (e.g., a laser transmitter). Light emitted by a LiDAR system is typically not in the visible spectrum; for example, infrared light is often used. Some of the light 604 b emitted encounters a physical object 608 (e.g., a vehicle) and reflects back to the LiDAR system 602. (Light emitted from a LiDAR system typically does not penetrate physical objects, e.g., physical objects in solid form.) The LiDAR system 602 also has one or more light detectors 610, which detect the reflected light. In an embodiment, one or more data processing systems associated with the LiDAR system generates an image 612 representing the field of view 614 of the LiDAR system. The image 612 includes information that represents the boundaries 616 of a physical object 608. In this way, the image 612 is used to determine the boundaries 616 of one or more physical objects near an AV.

FIG. 7 shows the LiDAR system 602 in operation. In the scenario shown in this figure, the AV 100 receives both camera system output 504 c in the form of an image 702 and LiDAR system output 504 a in the form of LiDAR data points 704. In use, the data processing systems of the AV 100 compares the image 702 to the data points 704. In particular, a physical object 706 identified in the image 702 is also identified among the data points 704. In this way, the AV 100 perceives the boundaries of the physical object based on the contour and density of the data points 704.

FIG. 8 shows the operation of the LiDAR system 602 in additional detail. As described above, the AV 100 detects the boundary of a physical object based on characteristics of the data points detected by the LiDAR system 602. As shown in FIG. 8 , a flat object, such as the ground 802, will reflect light 804 a-d emitted from a LiDAR system 602 in a consistent manner. Put another way, because the LiDAR system 602 emits light using consistent spacing, the ground 802 will reflect light back to the LiDAR system 602 with the same consistent spacing. As the AV 100 travels over the ground 802, the LiDAR system 602 will continue to detect light reflected by the next valid ground point 806 if nothing is obstructing the road. However, if an object 808 obstructs the road, light 804 e-f emitted by the LiDAR system 602 will be reflected from points 810 a-b in a manner inconsistent with the expected consistent manner. From this information, the AV 100 can determine that the object 808 is present.

Path Planning

FIG. 9 shows a block diagram 900 of the relationships between inputs and outputs of a planning module 404 (e.g., as shown in FIG. 4 ). In general, the output of a planning module 404 is a route 902 from a start point 904 (e.g., source location or initial location), and an end point 906 (e.g., destination or final location). The route 902 is typically defined by one or more segments. For example, a segment is a distance to be traveled over at least a portion of a street, road, highway, driveway, or other physical area appropriate for automobile travel. In some examples, e.g., if the AV 100 is an off-road capable vehicle such as a four-wheel-drive (4WD) or all-wheel-drive (AWD) car, SUV, pick-up truck, or the like, the route 902 includes “off-road” segments such as unpaved paths or open fields.

In addition to the route 902, a planning module also outputs lane-level route planning data 908. The lane-level route planning data 908 is used to traverse segments of the route 902 based on conditions of the segment at a particular time. For example, if the route 902 includes a multi-lane highway, the lane-level route planning data 908 includes trajectory planning data 910 that the AV 100 can use to choose a lane among the multiple lanes, e.g., based on whether an exit is approaching, whether one or more of the lanes have other vehicles, or other factors that vary over the course of a few minutes or less. Similarly, in some implementations, the lane-level route planning data 908 includes speed constraints 912 specific to a segment of the route 902. For example, if the segment includes pedestrians or un-expected traffic, the speed constraints 912 may limit the AV 100 to a travel speed slower than an expected speed, e.g., a speed based on speed limit data for the segment.

In an embodiment, the inputs to the planning module 404 includes database data 914 (e.g., from the database module 410 shown in FIG. 4 ), current location data 916 (e.g., the AV position 418 shown in FIG. 4 ), destination data 918 (e.g., for the destination 412 shown in FIG. 4 ), and object data 920 (e.g., the classified objects 416 as perceived by the perception module 402 as shown in FIG. 4 ). In some embodiments, the database data 914 includes rules used in planning. Rules are specified using a formal language, e.g., using Boolean logic. In any given situation encountered by the AV 100, at least some of the rules will apply to the situation. A rule applies to a given situation if the rule has conditions that are met based on information available to the AV 100, e.g., information about the surrounding environment. Rules can have priority. For example, a rule that says, “if the road is a freeway, move to the leftmost lane” can have a lower priority than “if the exit is approaching within a mile, move to the rightmost lane.”

FIG. 10 shows a directed graph 1000 used in path planning, e.g., by the planning module 404 (FIG. 4 ). In general, a directed graph 1000 like the one shown in FIG. 10 is used to determine a path between any start point 1002 and end point 1004. In real-world terms, the distance separating the start point 1002 and end point 1004 may be relatively large (e.g, in two different metropolitan areas) or may be relatively small (e.g., two intersections abutting a city block or two lanes of a multi-lane road).

In an embodiment, the directed graph 1000 has nodes 1006 a-d representing different locations between the start point 1002 and the end point 1004 that could be occupied by an AV 100. In some examples, e.g., when the start point 1002 and end point 1004 represent different metropolitan areas, the nodes 1006 a-d represent segments of roads. In some examples, e.g., when the start point 1002 and the end point 1004 represent different locations on the same road, the nodes 1006 a-d represent different positions on that road. In this way, the directed graph 1000 includes information at varying levels of granularity. In an embodiment, a directed graph having high granularity is also a subgraph of another directed graph having a larger scale. For example, a directed graph in which the start point 1002 and the end point 1004 are far away (e.g., many miles apart) has most of its information at a low granularity and is based on stored data, but also includes some high granularity information for the portion of the graph that represents physical locations in the field of view of the AV 100.

The nodes 1006 a-d are distinct from objects 1008 a-b which cannot overlap with a node. In an embodiment, when granularity is low, the objects 1008 a-b represent regions that cannot be traversed by automobile, e.g., areas that have no streets or roads. When granularity is high, the objects 1008 a-b represent physical objects in the field of view of the AV 100, e.g., other automobiles, pedestrians, or other entities with which the AV 100 cannot share physical space. In an embodiment, some or all of the objects 1008 a-b are a static objects (e.g., an object that does not change position such as a street lamp or utility pole) or dynamic objects (e.g., an object that is capable of changing position such as a pedestrian or other car).

The nodes 1006 a-d are connected by edges 1010 a-c. If two nodes 1006 a-b are connected by an edge 1010 a, it is possible for an AV 100 to travel between one node 1006 a and the other node 1006 b, e.g., without having to travel to an intermediate node before arriving at the other node 1006 b. (When we refer to an AV 100 traveling between nodes, we mean that the AV 100 travels between the two physical positions represented by the respective nodes.) The edges 1010 a-c are often bidirectional, in the sense that an AV 100 travels from a first node to a second node, or from the second node to the first node. In an embodiment, edges 1010 a-c are unidirectional, in the sense that an AV 100 can travel from a first node to a second node, however the AV 100 cannot travel from the second node to the first node. Edges 1010 a-c are unidirectional when they represent, for example, one-way streets, individual lanes of a street, road, or highway, or other features that can only be traversed in one direction due to legal or physical constraints.

In an embodiment, the planning module 404 uses the directed graph 1000 to identify a path 1012 made up of nodes and edges between the start point 1002 and end point 1004.

An edge 1010 a-c has an associated cost 1014 a-b. The cost 1014 a-b is a value that represents the resources that will be expended if the AV 100 chooses that edge. A typical resource is time. For example, if one edge 1010 a represents a physical distance that is twice that as another edge 1010 b, then the associated cost 1014 a of the first edge 1010 a may be twice the associated cost 1014 b of the second edge 1010 b. Other factors that affect time include expected traffic, number of intersections, speed limit, etc. Another typical resource is fuel economy. Two edges 1010 a-b may represent the same physical distance, but one edge 1010 a may require more fuel than another edge 1010 b, e.g., because of road conditions, expected weather, etc.

When the planning module 404 identifies a path 1012 between the start point 1002 and end point 1004, the planning module 404 typically chooses a path optimized for cost, e.g., the path that has the least total cost when the individual costs of the edges are added together.

Autonomous Vehicle Control

FIG. 11 shows a block diagram 1100 of the inputs and outputs of a control module 406 (e.g., as shown in FIG. 4 ). A control module operates in accordance with a controller 1102 which includes, for example, one or more processors (e.g., one or more computer processors such as microprocessors or microcontrollers or both) similar to processor 304, short-term and/or long-term data storage (e.g., memory random-access memory or flash memory or both) similar to main memory 306, ROM 308, and storage device 310, and instructions stored in memory that carry out operations of the controller 1102 when the instructions are executed (e.g., by the one or more processors).

In an embodiment, the controller 1102 receives data representing a desired output 1104. The desired output 1104 typically includes a velocity, e.g., a speed and a heading. The desired output 1104 can be based on, for example, data received from a planning module 404 (e.g., as shown in FIG. 4 ). In accordance with the desired output 1104, the controller 1102 produces data usable as a throttle input 1106 and a steering input 1108. The throttle input 1106 represents the magnitude in which to engage the throttle (e.g., acceleration control) of an AV 100, e.g., by engaging the steering pedal, or engaging another throttle control, to achieve the desired output 1104. In some examples, the throttle input 1106 also includes data usable to engage the brake (e.g., deceleration control) of the AV 100. The steering input 1108 represents a steering angle, e.g., the angle at which the steering control (e.g., steering wheel, steering angle actuator, or other functionality for controlling steering angle) of the AV should be positioned to achieve the desired output 1104.

In an embodiment, the controller 1102 receives feedback that is used in adjusting the inputs provided to the throttle and steering. For example, if the AV 100 encounters a disturbance 1110, such as a hill, the measured speed 1112 of the AV 100 is lowered below the desired output speed. In an embodiment, any measured output 1114 is provided to the controller 1102 so that the necessary adjustments are performed, e.g., based on the differential 1113 between the measured speed and desired output. The measured output 1114 includes measured position 1116, measured velocity 1118, (including speed and heading), measured acceleration 1120, and other outputs measurable by sensors of the AV 100.

In an embodiment, information about the disturbance 1110 is detected in advance, e.g., by a sensor such as a camera or LiDAR sensor, and provided to a predictive feedback module 1122. The predictive feedback module 1122 then provides information to the controller 1102 that the controller 1102 can use to adjust accordingly. For example, if the sensors of the AV 100 detect (“see”) a hill, this information can be used by the controller 1102 to prepare to engage the throttle at the appropriate time to avoid significant deceleration.

FIG. 12 shows a block diagram 1200 of the inputs, outputs, and components of the controller 1102. The controller 1102 has a speed profiler 1202 which affects the operation of a throttle/brake controller 1204. For example, the speed profiler 1202 instructs the throttle/brake controller 1204 to engage acceleration or engage deceleration using the throttle/brake 1206 depending on, e.g., feedback received by the controller 1102 and processed by the speed profiler 1202.

The controller 1102 also has a lateral tracking controller 1208 which affects the operation of a steering controller 1210. For example, the lateral tracking controller 1208 instructs the steering controller 1210 to adjust the position of the steering angle actuator 1212 depending on, e.g., feedback received by the controller 1102 and processed by the lateral tracking controller 1208.

The controller 1102 receives several inputs used to determine how to control the throttle/brake 1206 and steering angle actuator 1212. A planning module 404 provides information used by the controller 1102, for example, to choose a heading when the AV 100 begins operation and to determine which road segment to traverse when the AV 100 reaches an intersection. A localization module 408 provides information to the controller 1102 describing the current location of the AV 100, for example, so that the controller 1102 can determine if the AV 100 is at a location expected based on the manner in which the throttle/brake 1206 and steering angle actuator 1212 are being controlled. In an embodiment, the controller 1102 receives information from other inputs 1214, e.g., information received from databases, computer networks, etc.

Navigating Multi-way Stop Intersections

FIGS. 13A-13L illustrate examples of AV 100 navigating a multi-way stop intersection in environment 190. In particular, FIGS. 13A-13D illustrate AV 100 navigating a multi-way stop intersection when another vehicle turns right into the same lane as AV 100, FIGS. 13E-13H illustrate AV 100 navigating a multi-way stop intersection when another vehicle turns left across the lane of AV 100, and FIGS. 13I-13L illustrate AV 100 turning left at a multi-way stop intersection into the lane of another vehicle.

As shown in FIG. 13A, AV 100 is stopped at a primary stopline 1308 of the intersection. The primary stopline 1308 is a real or virtual line where a vehicle is expected to stop at the intersection. For example, the primary stopline 1308 corresponds to the expected stopping position as designated by stop sign 1304 and stop road marking 1306. Based on destination of AV 100, AV system 120 determines a planned travel path 1310 of AV 100 through the intersection (e.g., a path the AV 100 is expected to take from the stopline 1308 to an exit of the intersection based on the destination of AV 100). The AV system 120 can also determine a travel lane 1312 corresponding to (e.g., overlapping, nearest to) the planned travel path 1310. In some embodiments, the travel lane 1312 corresponds to one or more lanes of the roadway where the AV 100 is planning to go.

As shown in FIG. 13A, two other vehicles 1302 a and 1302 b are also at or near the multi-way stop intersection. Based on local traffic regulations, vehicle 1302 a has the precedence at the intersection (e.g., vehicle 1302 a arrived at the intersection before vehicle 1302 b and AV 100). When a vehicle has the highest precedence, it is expected to proceed into the intersection before vehicles with lower precedences, based on the local traffic regulations (e.g., the highest precedence vehicle arrived at the intersection before other vehicles at the intersection; the highest precedence vehicle is on the right of another vehicle that arrived at the intersection at approximately the same time; the highest precedence vehicle is going straight and another vehicle that arrived at the intersection at approximately the same time is turning).

AV system 120 determines that vehicle 1302 a has the highest precedence and determines an expected travel path 1314 of vehicle 1302 a. If vehicle 1302 a is stopped (or moving at less than a predetermined speed) and not indicating a turn with a turn signal, then AV system 120 initially determines the expected travel path 1314 of vehicle 1302 a will be straight toward the intersection. As shown in FIG. 13A, expected travel path 1314 will cause vehicle 1302 a to intersect travel lane 1312 of AV 100.

As shown in FIG. 13B, in response to the determination that the expected travel path 1314 of vehicle 1302 a will cause vehicle 1302 a to intersect travel lane 1312 of AV 100, the AV system 120 instructs AV 100 to wait at the primary stopline 1308. AV 100 waits at the primary stopline 1308 until AV system 120 determines that the planned travel path 1310 of AV 100 satisfies a set of one or more clearance criteria. The clearance criteria include a criterion that is satisfied when AV 100 is clear to safely merge into the travel lane 1312 without blocking the travel path of another vehicle (e.g., when AV 100 can join travel lane 1312 at a safe distance behind vehicle 1302 a without blocking paths of other vehicles).

While AV 100 waits at the primary stopline 1308, AV system 120 updates the expected travel path 1314 of vehicle 1302 a based on the movement of vehicle 1302 a. As shown in FIG. 13B, vehicle 1302 a is turning into the travel lane 1312 of AV 100 and the expected travel path 1314 is updated to correspond to the turn. In some embodiments, AV system 120 determines the trajectory of vehicle 1302 a and updates the expected travel path 1314 of vehicle 1302 a based on trajectory. In some embodiments, AV system 120 determines when vehicle 1302 a is expected to exit the intersection based on the trajectory.

As shown in FIG. 13C, once AV system 120 detects that the AV 100 is clear to safely merge into the travel lane 1312, AV system 120 instructs AV 100 to proceed past the primary stopline 1308. In some embodiments, before proceeding into the intersection, AV 100 stops (or slows) at a secondary stopline 1316. In some embodiments, the secondary stopline 1316 corresponds to the near edge of the intersection. Moving past the primary stopline 1308 to the secondary stopline 1316 before vehicle 1302 a has exited the intersection indicates to other vehicles (e.g., vehicle 1302 b) that AV 100 intends to proceed into the intersection. In some embodiments, when AV system 120 instructs AV 100 to AV proceed past the primary stopline 1308 to the secondary stopline 1316, AV 100 is instructed to accelerate with a predefined speed for indicating intent to proceed through intersection (e.g., a crawling speed that indicates AV 100 will be next to go through the intersection).

While AV 100 is at the secondary stopline 1316, AV system 120 confirms that AV 100 is clear to safely merge into travel lane 1312 (e.g., no other vehicles are expected to intersect travel lane 1312). If another vehicle is detected that poses a risk (e.g., a vehicle not currently at the multi-way stop intersection that is traveling at a speed high enough that it is not expected to stop at the intersection), AV system 120 instructs AV 100 to wait at the secondary stopline 1316 until AV 100 is clear to safely merge into the travel lane 1312. In some embodiments, AV system 120 determines whether any potential travel paths of undetected vehicles (e.g., virtual vehicles that AV system 120 determines to be traveling toward intersection but cannot physically detect) would prevent AV 100 from safely merging into travel lane 1312.

In some embodiments, AV system 120 filters (e.g., disregards, ignores) other vehicles with expected travel paths that do not intersect with the travel lane of the AV 100 (e.g., AV system 120 filters vehicle 1302 b when determining whether AV 100 should proceed past the secondary stopline 1316). In some embodiments, AV system 120 filters other vehicles moving below a threshold velocity or acceleration (e.g., AV system 120 disregards another vehicle that is crawling at a slow speed toward the intersection).

As shown in FIG. 13D, after AV system 120 determines AV 100 can safely merge into travel lane 1312, AV system 120 instructs AV 100 to proceed past the secondary stopline 1316. In some embodiments, AV system 120 confirms AV 100 is clear to safely merge into travel lane 1312 and instructs AV 100 to proceed past the secondary stopline 1316 without the AV 100 stopping at the secondary stopline 1316. In some embodiments, AV system 120 determines that AV 100 is clear to safely merge into travel lane 1312 when a distance between AV 100 and another vehicle (e.g., vehicle 1302 a) traveling in the same direction in the travel lane 1312 is greater than a threshold distance. In some embodiments, when AV system 120 instructs AV 100 to proceed past the secondary stopline 1316, AV 100 is instructed to accelerate with a predefined acceleration profile through the intersection (e.g., a normal acceleration profile used with a standard “go” command).

FIG. 13E illustrates AV 100 waiting at primary stopline 1308 while two other vehicles 1302 c and 1302 d are also at or near the multi-way stop intersection. Based on local traffic regulations, vehicle 1302 c has the precedence at the intersection (e.g., vehicle 1302 c arrived at the intersection before vehicle 1302 d and AV 100). AV system 120 determines that vehicle 1302 a has the highest precedence and determines an expected travel path 1314 of vehicle 1302 a. In some embodiments, the expected travel path 1314 of vehicle 1302 c is based in part on detecting a turn indicator of vehicle 1302 c. In the embodiment shown in FIG. 13E, a left turn indicator of vehicle 1302 c is detected, AV system 120 determines that the expected travel path 1314 will cause vehicle 1302 c to intersect the travel lane 1312 of AV 100. If AV 100 were to proceed into the intersection before vehicle 1302 c completes the turn, AV 100 would block the expected travel path 1314 of vehicle 1302 c. In some embodiments, AV system 120 determines that AV 100 would block the expected travel path of another vehicle when the other vehicle is expected to change speed by more than a threshold change in speed to avoid colliding with AV 100 (e.g., when the other vehicle is expected to decelerate by more than 3.2 m/s′ to avoid colliding).

As shown in FIG. 13F, in response to the determination that the expected travel path 1314 of vehicle 1302 c will cause vehicle 1302 c to intersect the travel lane 1312 of AV 100, AV system 120 instructs AV 100 to wait at the primary stopline 1308. AV 100 waits at the primary stopline 1308 until AV system 120 determines that the planned travel path 1310 of AV 100 satisfies a set of one or more clearance criteria. The clearance criteria include a criterion that is satisfied when AV 100 is clear to safely proceed along the travel lane 1312 without blocking the travel path of another vehicle (e.g., when AV 100 can join the travel lane 1312 without blocking the travel path of vehicle 1302 c).

While AV 100 waits at the primary stopline 1308, AV system 120 updates the expected travel path 1314 of vehicle 1302 c based on the movement of vehicle 1302 c (e.g., vehicle 1302 c is expected to continue turning in the same direction). As shown in FIG. 13F, vehicle 1302 c is turning left across the travel lane 1312 of AV 100 and the expected travel path 1314 is updated to correspond to the turn. In some embodiments, AV system 120 determines the trajectory of vehicle 1302 c and updates the expected travel path 1314 of vehicle 1302 a based on trajectory. In some embodiments, the AV system 120 determines when vehicle 1302 c is expected to exit the intersection based on the trajectory.

As shown in FIG. 13G, once AV system 120 detects that the expected travel path 1314 of vehicle 1302 c will cause vehicle 1302 c to exit the travel lane 1312 (e.g., before vehicle 1302 c has exited the intersection), AV system 120 instructs AV 100 to proceed past the primary stopline 1308. In some embodiments, before proceeding into the intersection, AV 100 stops (or slows) at a secondary stopline 1316 corresponding to the near edge of the intersection. Moving past the primary stopline 1308 to the secondary stopline 1316 before vehicle 1302 c has exited the intersection indicates to other vehicles (e.g., vehicle 1302 d) that AV 100 intends to proceed into the intersection. In some embodiments, when AV system 120 instructs AV 100 to AV proceed past the primary stopline 1308 to the secondary stopline 1316, the AV 100 is instructed to accelerate with a predefined speed for indicating intent to proceed through intersection (e.g., a crawling speed that indicates the AV 100 will be next to go through the intersection).

While stopped at or proceeding toward the secondary stopline 1316, AV system 120 confirms that AV 100 is clear to safely merge into travel lane 1312 (e.g., no other vehicles are expected to intersect the travel lane 1312). If another vehicle is detected that poses a risk (e.g., a vehicle not currently at the multi-way stop intersection that is traveling at a speed high enough that it is not expected to stop at the intersection), AV system 120 instructs AV 100 to wait at the secondary stopline 1316 until AV 100 is clear to safely merge into the travel lane 1312. In some embodiments, AV system 120 determines whether any potential travel paths of undetected vehicles (e.g., virtual vehicles that AV system 120 determines to be traveling toward intersection but cannot physically detect) would prevent AV 100 from safely merging into the travel lane 1312.

As shown in FIG. 13H, after AV system 120 determines AV 100 can safely merge into the travel lane 1312 (e.g., vehicle 1302 c has exited the travel lane 1312), AV system 120 instructs AV 100 to proceed past the secondary stopline 1316. In some embodiments, AV system 120 confirms AV 100 is clear to safely merge into the travel lane 1312 and instructs AV 100 to proceed past the secondary stopline 1316 without AV 100 stopping at the secondary stopline 1316. In some embodiments, when AV system 120 instructs AV 100 to proceed past the secondary stopline 1316, AV 100 is instructed to accelerate with a predefined acceleration profile through the intersection (e.g., a normal acceleration profile used with a standard “go” command).

FIG. 13I illustrates AV 100 waiting at primary stopline 1308 while another vehicle 1302 e is at or near the multi-way stop intersection. As shown in FIG. 13I, the planned travel path 1310 of AV 100 has AV 100 turning left through the multi-way stop intersection. Based on the planned travel path 1310, travel lane 1312 of AV 100 includes the current lane of the roadway where the AV 100 is waiting at stopline 1308 and a perpendicular lane of the roadway (e.g. the lane vehicle 1302 e is facing).

Based on local traffic regulations, vehicle 1302 e has the precedence at the intersection (e.g., vehicle 1302 e arrived at the intersection before AV 100). AV system 120 determines that vehicle 1302 e has the highest precedence and determines an expected travel path 1314 of vehicle 1302 e. As shown in FIG. 13I, AV system 120 initially determines the expected travel path 1314 of vehicle 1302 e will be straight toward the intersection, which will cause vehicle 1302 e to intersect the travel lane 1312 of AV 100.

As shown in FIG. 13J, in response to the determination that the expected travel path 1314 of vehicle 1302 e will cause vehicle 1302 e to intersect travel lane 1312 of AV 100, AV 100 waits at the primary stopline 1308. AV 100 waits at the primary stopline 1308 until AV system 120 determines that the planned travel path 1310 of AV 100 satisfies a set of one or more clearance criteria. The clearance criteria include a criterion that is satisfied when AV 100 is clear to safely merge into the travel lane 1312 without blocking the travel path of another vehicle (e.g., when AV 100 can join the travel lane 1312 at a safe distance behind vehicle 1302 e without blocking paths of other vehicles).

While AV 100 waits at the primary stopline 1308, AV system 120 updates the expected travel path 1314 of vehicle 1302 c based on the movement of vehicle 1302 e. As shown in FIG. 13J, vehicle 1302 e is continuing straight into the travel lane 1312 of AV 100 and the expected travel path 1314 is updated based on the continued direction of travel. In some embodiments, AV system 120 determines the trajectory of vehicle 1302 e and updates the expected travel path 1314 of vehicle 1302 a based on trajectory. In some embodiments, AV system 120 determines when vehicle 1302 e is expected to exit the intersection based on the trajectory.

As shown in FIG. 13K, once AV system 120 detects that the AV 100 is clear to safely proceed along the travel lane 1312, AV system 120 instructs AV 100 to proceed past the primary stopline 1308. In some embodiments, before proceeding into the intersection, AV 100 stops (or slows) at a secondary stopline 1316 corresponding to the near edge of the intersection. Moving past the primary stopline 1308 to the secondary stopline 1316 before vehicle 1302 e has exited the intersection indicates to other vehicles that AV 100 intends to proceed into the intersection. In some embodiments, when AV system 120 instructs AV 100 to proceed past the primary stopline 1308 to the secondary stopline 1316, AV 100 is instructed to accelerate with a predefined speed for indicating intent to proceed through intersection (e.g., a crawling speed that indicates the AV 100 will be next to go through the intersection).

While stopped at the secondary stopline 1316, AV system 120 confirms that AV 100 is clear to safely merge into the travel lane 1312 (e.g., no other vehicles are expected to intersect the travel lane 1312). If another vehicle is detected that poses a risk (e.g., a vehicle not currently at the multi-way stop intersection that is traveling at a speed high enough that it is not expected to stop at the intersection), AV system 120 instructs AV 100 to wait at the secondary stopline 1316 until AV 100 is clear to safely merge into the travel lane 1312. In some embodiments, AV system 120 determines whether any potential travel paths of undetected vehicles (e.g., virtual vehicles that AV system 120 determines to be traveling toward intersection but cannot physically detect) would prevent AV 100 from safely merging into the travel lane 1312.

As shown in FIG. 13L, after AV system 120 determines AV 100 can safely merge into the travel lane 1312, AV system 120 instructs AV 100 to proceed past the secondary stopline 1316. In some embodiments, AV system 120 confirms AV 100 is clear to safely merge into the travel lane 1312 and instructs AV 100 to proceed past the secondary stopline 1316 without AV 100 stopping at the secondary stopline 1316. In some embodiments, AV system 120 determines that AV 100 is clear to safely merge into the travel lane 1312 when a distance between the AV 100 and another vehicle (e.g., vehicle 1302 e) traveling in the same direction in the travel lane 1312 is greater than a threshold distance. In some embodiments, when AV system 120 instructs AV 100 to proceed past the secondary stopline 1316, AV 100 is instructed to accelerate with a predefined acceleration profile through the intersection (e.g., a normal acceleration profile used with a standard “go” command).

Example Processes for Navigating a Multi-Way Stop Intersection

FIG. 14 is a flow chart of an example process 1400 for navigating a multi-way stop intersection. For convenience, the process 1400 will be described as being performed by a system of one or more computers located in one or more locations. For example, the AV system 120 of FIG. 1 (or portions thereof), appropriately programmed in accordance with this specification, can perform the process 1400.

At block 1402, while a first vehicle (e.g., AV 100) is operating in an autonomous mode (e.g., a fully or highly autonomous mode with automated steering, acceleration, braking, and navigation (e.g., Level 3, 4, or 5)), the system (e.g., AV system 120) detects, using a processing circuit, the first vehicle is at a primary stopline (e.g., 1308) (e.g., a real or virtual line where a vehicle is expected to stop at an intersection (e.g., at the stop sign), a line corresponding to the near edge of the intersection) of a multi-way stop intersection.

At block 1404, the system obtains, using the processing circuit, a planned travel path though the multi-way stop intersection (e.g., 1310) (e.g., a path the AV 100 is expected to take from the stopline 1308 to an exit of the intersection based on the destination of the AV and current road conditions). In some embodiments, the multi-way stop intersection includes a secondary stopline (e.g., 1316) in the planned travel path of the first vehicle. In some embodiments, the secondary stopline corresponds to an edge of the multi-way stop intersection.

In some embodiments, at block 1406, the system detects, using the processing circuit, one or more other vehicles (e.g., 1302 a-1302 e) at one or more tertiary stoplines (e.g., real or virtual lines where other vehicles are expected to stop at the intersection (e.g., at other stop signs)) of the multi-way stop intersection.

At block 1408, the system determines whether the first vehicle has a higher precedence than the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection (e.g., the AV 100 is the next vehicle to have the right-of-way according to local traffic rules (e.g., the first vehicle arrived at the intersection before other vehicles at the intersection; the first vehicle is to the right of another vehicle that arrived at the intersection at approximately the same time; the first vehicle going straight and another vehicle that arrived at the intersection at approximately the same time is turning).

At block 1410, the system determines whether the planned travel path of the first vehicle through the multi-way stop intersection satisfies a set of one or more clearance criteria. The set of one or more clearance criteria include a criterion that is satisfied in response to detecting the first vehicle is clear to safely merge into a travel lane (e.g., 1312) (e.g., a lane of the roadway where vehicles travel in the direction the AV 100 is planning to go) corresponding to (e.g., overlapping, nearest to) the planned travel path (e.g., the AV 100 can join the travel lane 1312 at a safe distance behind another vehicle traveling along the same path, and without blocking paths of other vehicles). In some embodiments, detecting the first vehicle is clear to safely merge into the travel lane includes detecting the first vehicle does not block an expected travel path of another vehicle. In some embodiments, the first vehicle does not block the expected travel path of another vehicle when the other vehicle is not expected to change speed by more than a threshold change in speed (e.g., the other vehicle is not expected to decelerate by more than 3.2 m/s²). In some embodiments, detecting the first vehicle is clear to safely merge into the travel lane includes detecting a distance between the first vehicle and another vehicle in the travel lane is greater than a threshold distance. In some embodiments, the expected travel path of the other vehicle corresponds to a potential travel path of an undetected vehicle (e.g., virtual vehicle that AV system 120 determines to be traveling toward intersection but cannot physically detect).

In some embodiments, the system detects, using the processing circuit, one or more other vehicles with expected travel paths that do not intersect with the travel lane of the first vehicle and filters (e.g., disregards, ignores), using the processing circuit, the one or more other vehicles from the determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies a set of one or more clearance criteria. In some embodiments, the set of one or more clearance criteria include a criterion that is not satisfied if another vehicle with a speed more than a threshold speed is detected approaching the multi-way stop intersection (e.g., other vehicle is traveling at a speed high enough that it is not expected to stop at its own stopline of the multi-stop intersection).

At block 1412, in accordance with a determination that the first vehicle has a higher precedence than the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection and in accordance with the determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies the set of one or more clearance criteria, the system instructs, using the control circuit, the first vehicle to proceed past the primary stopline (e.g., travel into the intersection, travel to another stopline (e.g., 1316) at a near edge of the intersection).

In some embodiments, after instructing the first vehicle to proceed past the primary stopline, the system detects, using the processing circuit, one or more other vehicles at one or more tertiary stoplines (e.g., real or virtual lines where other vehicles are expected to stop at the intersection (e.g., at other stop signs)) of the multi-way stop intersection. In accordance with a determination that the first vehicle has a higher precedence than the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection (e.g., the AV 100 is the next vehicle to have the right-of-way according to local traffic rules) and in accordance with the determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies the set of one or more clearance criteria, the system instructs, using the control circuit, the first vehicle to proceed past the secondary stopline. In accordance with a determination that the first vehicle does not have a higher precedence than at least one of the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection or in accordance with a determination that the planned travel path of the first vehicle through the multi-way stop intersection does not satisfy the set of one or more clearance criteria, the system instructs, using the control circuit, the first vehicle to forgo proceeding past the secondary stopline (e.g., the AV 100 waits at the secondary stopline 1316). In some embodiments, instructing the first vehicle to forgo proceeding past the secondary stopline includes instructing the first vehicle to stop at the secondary stopline.

At block 1414, in accordance with a determination that the first vehicle does not have a higher precedence than at least one of the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection or in accordance with a determination that the planned travel path of the first vehicle through the multi-way stop intersection does not satisfy the set of one or more clearance criteria, the system instructs, using the control circuit, the first vehicle to forgo proceeding past the primary stopline (e.g., the AV 100 waits at the primary stopline 1308).

FIG. 15 is a flow chart of an example process 1500 for navigating a multi-way stop intersection. For convenience, the process 1500 will be described as being performed by a system of one or more computers located in one or more locations. For example, the AV system 120 of FIG. 1 (or portions thereof), appropriately programmed in accordance with this specification, can perform the process 1500.

At block 1502, while a first vehicle (e.g., AV 100) is operating in an autonomous mode (e.g., a fully or highly autonomous mode with automated steering, acceleration, braking, and navigation (e.g., Level 3, 4, or 5)) at a multi-way stop intersection and has a highest precedence (e.g., the AV 100 is the next vehicle to have the right-of-way according to local traffic rules (e.g., the first vehicle arrived at the intersection before other vehicles at the intersection; the first vehicle is to the right of another vehicle that arrived at the intersection at approximately the same time; the first vehicle going straight and another vehicle that arrived at the intersection at approximately the same time is turning)) at the multi-way stop intersection, the system (e.g., AV system 120) detects, using a processing circuit, movement of a second vehicle (e.g., 1302 a-1302 e) at the intersection (e.g., at or near a stop sign; in the intersection at an area where travel paths intersect). In some embodiments, detecting the movement of the second vehicle includes detecting a velocity of the second vehicle, and in accordance with a determination that the velocity of the second vehicle is below a threshold velocity (e.g., the other vehicle is crawling toward intersection), the system instructs, using the control circuit, the first vehicle to proceed into the intersection. In some embodiments, in accordance with a determination that the velocity of the second vehicle is at or above the threshold velocity, the system forgoes instructing the first vehicle to proceed into the intersection. In some embodiments, detecting the movement of the second vehicle includes detecting an acceleration of the second vehicle, and in accordance with a determination that the acceleration of the second vehicle is below a threshold acceleration (e.g., the other vehicle is crawling toward intersection), the system instructs, using the control circuit, the first vehicle to proceed into the intersection. In some embodiments, in accordance with a determination that the acceleration of the second vehicle is at or above the threshold acceleration, the system forgoes instructing the first vehicle to proceed into the intersection.

At block 1504, the system determines the second vehicle has an expected travel path (e.g., 1314) through the intersection that intersects a planned travel path (e.g., 1310) of the first vehicle through the intersection (e.g., based on detecting a turn signal of the second vehicle, based on a calculated trajectory of the second vehicle).

At block 1506, in accordance with a determination, based on the detected movement of the second vehicle, that the second vehicle is expected to exit the intersection (e.g., before the first vehicle can reach a point on the expected travel path of the second vehicle) (e.g., proceeding into the intersection by the first vehicle will not cause a collision with the second vehicle based on the expected and planned travel paths), the system instructs, using a control circuit, the first vehicle to proceed into the intersection before the second vehicle exits the intersection. In some embodiments, the determination, based on the detected movement of the second vehicle, that the second vehicle is expected to exit the intersection includes determining the trajectory of the second vehicle. In some embodiments, in accordance with a determination that the trajectory of the second vehicle does not intersect an expected trajectory of the first vehicle, the system instructs, using the control circuit, the first vehicle to proceed into the intersection before the second vehicle exits the intersection.

In some embodiments, after proceeding into the intersection and in accordance with a determination that the trajectory of the second vehicle intersects an expected trajectory of the first vehicle, the system instructs, using the control circuit, the first vehicle to stop before the first vehicle exits the intersection (e.g., after beginning movement toward intersection, the AV 100 stops if a trajectory of another vehicle predicted to intersect with the AV's trajectory). In some embodiments, instructing the first vehicle to proceed into the intersection includes instructing the first vehicle to accelerate with a predefined acceleration curve through the intersection (e.g., a normal acceleration curve used with standard “go” command). In some embodiments, instructing the first vehicle to proceed into the intersection includes instructing the first vehicle to proceed with a predefined speed for indicating intent to proceed through intersection (e.g., a crawling speed that indicates the first vehicle will be next to go through intersection). In some embodiments, after instructing the first vehicle to proceed with the predefined speed for indicating intent, the system instructs, using the control circuit, the first vehicle to accelerate with a predefined acceleration curve (e.g., a normal acceleration curve used with standard “go” command).

In the foregoing description, embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. The description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the claims, and what is intended by the applicants to be the scope of the claims, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. In addition, when we use the term “further comprising,” in the foregoing description or following claims, what follows this phrase can be an additional step or entity, or a sub-step/sub-entity of a previously-recited step or entity. 

What is claimed is:
 1. A system, comprising: one or more computer processors; and one or more non-transitory storage media storing instructions which, when executed by the one or more computer processors while a first vehicle is operating in an autonomous mode, cause performance of operations comprising: detecting the first vehicle is at a primary stopline of a multi-way stop intersection; obtaining a planned travel path through the multi-way stop intersection; and in response to detecting that the first vehicle is at a primary stopline of a multi-way stop intersection: detecting one or more other vehicles at one or more tertiary stoplines of the multi-way stop intersection; and in accordance with i) a determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies a set of one or more clearance criteria, and ii) a determination that the first vehicle has a higher precedence than the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection, instructing the first vehicle to proceed past the primary stopline and stop at a secondary stopline before entering the multi-way stop intersection to indicate an intent of the first vehicle to proceed through the multi-way stop intersection, wherein the set of one or more clearance criteria include a criterion that is satisfied in response to detecting the first vehicle is clear to safely merge into a travel lane corresponding to the planned travel path.
 2. The system of claim 1, wherein detecting the first vehicle is clear to safely merge into the travel lane includes detecting the first vehicle does not block an expected travel path of another vehicle.
 3. The system of claim 2, wherein the first vehicle does not block the expected travel path of another vehicle when the another vehicle is not expected to change speed by more than a threshold change in speed.
 4. The system of claim 1, wherein detecting the first vehicle is clear to safely merge into the travel lane includes detecting a distance between the first vehicle and another vehicle in the travel lane is greater than a threshold distance.
 5. The system of claim 2, wherein the expected travel path of the another vehicle corresponds to a potential travel path of an undetected vehicle.
 6. The system of claim 1, wherein the secondary stopline corresponds to an edge of the multi-way stop intersection.
 7. The system of claim 1, wherein the instructions further cause performance of operations comprising: after instructing the first vehicle to proceed past the primary stopline: detecting one or more other vehicles at one or more tertiary stoplines of the multi-way stop intersection; and in accordance with a determination that the first vehicle has a higher precedence than the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection and in accordance with the determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies the set of one or more clearance criteria, instructing the first vehicle to proceed past the secondary stopline.
 8. The system of claim 1, wherein the instructions further cause performance of operations comprising: detecting one or more other vehicles with expected travel paths that do not intersect with the travel lane of the first vehicle; and filtering the one or more other vehicles from the determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies a set of one or more clearance criteria.
 9. The system of claim 1, wherein the set of one or more clearance criteria include a criterion that is not satisfied if another vehicle with a speed more than a threshold speed is detected approaching the multi-way stop intersection.
 10. A method, comprising: while a first vehicle is operating in an autonomous mode: detecting, using a processing circuit, the first vehicle is at a primary stopline of a multi-way stop intersection; obtaining, using the processing circuit, a planned travel path through the multi-way stop intersection; and in response to detecting that the first vehicle is at a primary stopline of a multi-way stop intersection: detecting one or more other vehicles at one or more tertiary stoplines of the multi-way stop intersection; and in accordance with: i) a determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies a set of one or more clearance criteria, and ii) a determination that the first vehicle has a higher precedence than the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection, instructing, using a control circuit, the first vehicle to proceed past the primary stopline and stop at a secondary stopline before entering the multi-way stop intersection to indicate an intent of the first vehicle to proceed through the multi-way stop intersection, wherein the set of one or more clearance criteria include a criterion that is satisfied in response to detecting the first vehicle is clear to safely merge into a travel lane corresponding to the planned travel path.
 11. The method of claim 10, wherein detecting the first vehicle is clear to safely merge into the travel lane includes detecting the first vehicle does not block an expected travel path of another vehicle.
 12. The method of claim 11, wherein the first vehicle does not block the expected travel path of another vehicle when the another vehicle is not expected to change speed by more than a threshold change in speed.
 13. The method of claim 10, wherein detecting the first vehicle is clear to safely merge into the travel lane includes detecting a distance between the first vehicle and another vehicle in the travel lane is greater than a threshold distance.
 14. The method of claim 10, wherein the secondary stopline corresponds to an edge of the multi-way stop intersection.
 15. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices while a first vehicle is operating in an autonomous mode, cause performance of operations comprising: detecting, using a processing circuit, the first vehicle is at a primary stopline of a multi-way stop intersection; obtaining, using the processing circuit, a planned travel path through the multi-way stop intersection; and in response to detecting that the first vehicle is at a primary stopline of a multi-way stop intersection: detecting one or more other vehicles at one or more tertiary stoplines of the multi-way stop intersection; and in accordance with: i) a determination that the planned travel path of the first vehicle through the multi-way stop intersection satisfies a set of one or more clearance criteria, and ii) a determination that the first vehicle has a higher precedence than the one or more other vehicles at the one or more tertiary stoplines of the multi-way stop intersection, instructing, using a control circuit, the first vehicle to proceed past the primary stopline and stop at a secondary stopline before entering the multi-way stop intersection to indicate an intent of the first vehicle to proceed through the multi-way stop intersection, wherein the set of one or more clearance criteria include a criterion that is satisfied in response to detecting the first vehicle is clear to safely merge into a travel lane corresponding to the planned travel path. 